1. Field of the Invention
The present invention relates to an input device and more particularly, to a key switch structure for input device, which uses two links arranged in a cross manner for performing a scissors action to support a key cap in balance, stabilizing vertical movement of the key cap when the key cap is clicked to drive a circuit module in producing a control signal. This simple design of key switch structure is suitable for mass production, lowering the manufacturing cost.
2. Description of the Related Art
Following fast development of computer-related technology, many practical and functional electronic products have been continuously created and have appeared on the market. Most commercial electronic products have an input device made in the form of a mouse, keyboard, joystick or light gun for data or command entry. For different applications, different input devices shall be used. For example, a keyboard for notebook computer is quite different from the configuration for desk computer. A notebook computer has light, thin, short and small characteristics. Therefore, the key switch structure of a keyboard for desk computer cannot be directly used in a keyboard for notebook computer. It must be specially configured to fit the requirements for notebook computer.
A conventional key switch structure for keyboard has a linking mechanism provided between a key cap and a bottom board to support vertical movement of the key cap. The linking mechanism may be made in the form of a cross-linkage (scissors-structure), rotary structure or sliding structure. FIG. 9 illustrates a key switch structure for input device according to the prior art. According to this design, the key switch structure comprises a bottom board C, a circuit board D supported on the bottom board C and carrying a rubber cone D1, a key cap B, and a linking mechanism A coupled between axle holders C1 of the bottom board C and axle holders B1 of the key cap B around the rubber cone D1. The linking mechanism A includes an inner link A1 and an outer link A2. The inner link A1 has two pivot pins A11 bilaterally disposed on the middle and respectively pivotally coupled to respective pivot holes A21 of the outer link A2. Further, the inner link A1 and the outer link A2 have the respective coupling rods A12 and A22 respectively coupled to the axle holders C1 of the bottom board C and the axle holders B1 of the key cap B. When a user clicks the key cap B, the rubber cone D1 is compressed to trigger the circuit board D, causing the circuit board D to output a control signal. At the same time, the inner link A1 and the outer link A2 are moved relative to each other to support vertical movement of the key cap B.
The aforesaid key switch structure is functional, however it still has drawbacks. The pivot pins A11 of the inner link A1 may be broken accidentally during installation by labor, or may break easily due to a stress concentration after a long use of the key switch structure. Further, the alignment between the pivot pins A11 of the inner link A1 and the pivot holes A21 of the outer link A2 is quite important. A small alignment error between the pivot pins A11 and the pivot holes A21 may result in vibration and malfunctioning of the linking mechanism during operation of the key switch structure. Further, the assembly procedure of this design key switch structure is complicated.